A COUPLE OF CLEANING BRUSH ROTARY INSIDE,ONE IS TO CLEAN P ROLLERS WHILE ANOTHER IS TO CLEAN C-P ROLLERS, ADJUST CHAIN WHELL AND CHAIN TO LET FRONT BRUSH CLEAN C-P ROLLERS AND REAR BRUSH CLEAN P ROLLERS. THE BRUSH HAVE TO BE 2-3MM PLUGING INTO FILLET AND TIGHTLY LOCKING EVERY BOLTS.